The present invention relates to an improved annulus pressure responsive sampling apparatus for use in the sampling of well formation fluids in the testing of oil wells.
Various tester valves, circulation valves and sampler valves for testing oil wells have been developed which are responsive to changes in the annulus pressure of the fluid between the well bore and the testing string for the opening and closing of the various valves. These various annulus pressure responsive valves are useful, particularly in offshore testing operations, where it is desired to manipulate the various valves in the testing string without utilizing reciprocation of the testing string thereby allowing the blow-out preventers to remain closed about the testing string.
Typical prior art annulus pressure responsive valves which may be used as sampler valves for obtaining a sample of the formation fluids during the formation testing procedure are described in U.S. Pat. Nos. 3,664,415; 3,858,649; 3,964,305; 4,047,564; 4,064,937 and 4,063,593. An example of an annulus pressure responsive valve which is used as a circulating valve in a formation testing string is described in U.S. Pat. No. 4,311,197.
Other types of sampler valves are described in U.S. Pat. No. 3,969,937 and in Halliburton Services Sales and Service Catalog Number 41 on pages 3986, 3987 and 3988 therein.
Also, in wells where high formation pressures and flow rates are encountered along with sour gas, hydrogen sulfide (H.sub.2 S), being present it is desirable to have an annulus pressure responsive sampler valve which is designed to catch and retrieve samples of formation fluids under such conditions. It is further desirable to have an annulus pressure responsive sampler valve which has an unrestricted bore therethrough after catching a sample of formation fluids so that formation fluids recovered during testing operations may be injected back into the formation or other operations may occur as desired. This is particularly desirable in environmentally sensitive areas where the surface disposal of formation fluids is a problem or prohibited.